290 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 40 



living in winter that is almost hibernation. If we will consider our own 

 feelings on many days when the weather is bad, we will see how easy 

 it might be to go into a partial hibernation even though we lack the 

 specialization that makes it possible for the furry creatures to hiber- 

 nate so successfully. 



Many animals that do not hibernate encounter more or less alter- 

 nating periods when food is abundant and when it is scarce. Some 

 of these have developed remarkable methods of providing for the lean 

 period. The stump-tailed lizard or shingle-back lizard {Tiliqua) of 

 Australia, the Gila monster {Heloderma suspectum) of the southwest- 

 ern United States and its relative, the beaded lizard {H. horridum) 

 of Mexico, lay up considerable masses of fat in their tails. These fat 

 masses become large enough to serve as reservoirs of energy during 

 periods when food is scarce. The camel carries his reservoir for 

 energy in his hump. If a camel's hump is erect and plump, it shows 

 that he is in good condition and should be able to stand a period of 

 food shortage without serious injury. If, however, his hump is flabby 

 it shows that he is not prepared to do without food or to go on short 

 rations, although he may be in satisfactory condition so far as day-to- 

 day living is concerned. 



The little fat-tailed lemur {Cheirogaleus) of Madagascar likewise 

 carries his reservoir of energy food in his tail which he greatly fattens 

 in seasons of plenty and draws upon in periods of scarcity. 



Some bats hibernate in caves, buildings, hollow trees, or other loca- 

 tions where they can obtain a fairly uniform temperature of about 

 46° to 54° F. Great numbers of bats are frequently found in such 

 locations. Other bats migrate like birds, but almost nothing is 

 known about the exact courses and dates of their movements. It can 

 merely be said that they go south to escape the winter and return 

 north in the spring; the details of their flights are yet to be discovered. 



Birds meet the problem of bad weather or food shortage in many 

 cases by migrating to a more equitable climate where food is available. 

 Before making the migration they become exceedingly fat : but when 

 their long journey is ended the fat supply is practically consumed 

 and they are often in an exhausted condition. 



SOCIABILITY, COOPERATION, PROPERTY AND TERRITORIAL RIGHTS 



Many animals are definitely gregarious and sociable; others lead 

 solitary lives. Still others mingle with their kind for short periods of 

 the year, but at other seasons prefer to be solitary. I believe it is 

 probable that the requirements of an adequate food supply have much 

 influence in determining whether animals must be solitary or may be 

 gregarious. In many cases it is obvious that animals enjoy compan- 

 ionship with their own kind or even with animals of other species. 



